Electrical power distribution busducts typically include an elongate duct containing a plurality of elongate flat electrically conductive busbars, for example three phase busbars, at least one neutral busbar and an earth busbar, separated by electrically insulating material. A busduct system usually includes a plurality of busduct sections coupled together to provide an appropriate length of busduct to connect one piece of electrical apparatus to another in lieu of cables.
One of the major considerations in designing a busduct system is the provision of a busduct joints for joining busduct sections together. The design of these joints presents a number of parameters to consider, including space and size limitations; accommodation of varying numbers of busbars within a single joint design; contact resistances within the joints; insulation break-down between busbars within the joints and arcing between the busbars; attachment of the joints to the busducts and maintenance of the organization of joint components during assembly and installation; and, in particular, the effective dissipation of heat from the conductors within the busduct joint. In addition to designing a joint which takes into account the above-listed design parameters, these parameters must be dealt with in a cost effective manner.
The effective dissipation of heat from a busduct section and from a busduct joint in particular is essential to achieving the testing parameters of the UL and IEC standards which outline the maximum temperature rise limit of electrically conductive material within the busduct joint.
Examples of known busduct joints are found in U.S. Pat. No. 5,068,763; U.S. Pat. No. 4,950,841; U.S. Pat. No. 4,849,581; U.S. Pat. No. 4,842,533; U.S. Pat. No. 4,705,334; U.S. Pat. No. 4,009,920; U.S. Pat. No. 3,786,394; U.S. Pat. No. 3,383,458; U.S. Pat. No. 3,365,537; U.S. Pat. Nos. 3,183,298; and 3,104,276, which are incorporated herein by reference in their entireties. A typical busduct joint including a fastening bolt surrounded by an insulated sleeve, where the fastening bolt extends through and holds together a stack of adjacent pairs of conductive splice plates and insulator plates. Busbars of adjacent busduct sections are inserted between the opposite ends of adjacent pairs of splice plates when the bolt is loosened. The bolt is then tightened to compress the assembly together and provide a tight engagement between the splice plates and corresponding busbars. Then top and bottom covers are installed once the bolt is torqued. Due to manufacturing tolerances the bolt must be quite loose during installation so that sufficient spacing is provided between pairs of splice plates to permit insertion of busbars. A problem with such existing busduct joints is the difficulty in dissipating heat from the tightly stacked splice plates and busbars within the busduct joint.